Miranda Hollander is a college professor who shares a home with her uncle, Tom Hollander, a museum worker, and she possesses a extraordinary ability: she can read books by touch without ever opening them. Raised with the belief that her parents died in an accident when she was a baby, she experiences a frightening turn after her birthday when she blackouts and is rushed to a local hospital. There, the calm of the hospital gives way to horror as Miranda transforms into an alien form and kills several people. When Tom arrives the next morning, he finds a scene of widespread death and quickly takes action to uncover the truth behind his niece’s condition.
Tom locates Miranda, injects her with human hormones, and drives her toward a remote, more controlled environment in Mexico. Along the way, Miranda awakens and asks for the cause of her illness. Tom reveals a disturbing origin: she is the product of an experiment that fused human and alien DNA, a project that Tom conducted with his former colleague, Forbes McGuire, during their college days. To keep Miranda safe and “normal,” Tom has been administering human hormones since childhood, a devious strategy designed to suppress her alien DNA. He also admits that Miranda’s supposed parents were a fiction created to shield her from the truth, a story he and Forbes concocted. The two men eventually parted ways over divergent visions for their creation, leaving Miranda’s fate in a precarious balance.
In Mexico, Tom and Miranda track down Forbes, who lives with a recent experiment of his own: Azura, a hybrid who combines human and alien DNA and who serves as Forbes’s assistant and lover. Forbes sustains his project by crafting half-alien replicas of dead pets and relatives for paying clients, a macabre echo of their early experimentation. Forbes confirms Miranda’s condition is dire; her body is fighting back with increasingly unstable alien characteristics, and the only apparent cure would be to inject fresh human DNA into her. Yet Miranda refuses, realizing that such a transfusion would amount to a human sacrifice. Unnerved, she slips into unconsciousness, and Tom is left to search for a donor, only to be mugged along the way. Azura intervenes, incapacitating the mugger, and the two return Miranda to Forbes’s lab, where they succeed in extending her life.
As time passes, Miranda’s behavior grows stranger. She makes unsettling jokes about sex with Azura, and Tom monitors her blood while she hints at intimacy in their hotel room; he urges rest, thinking the delirium is the result of the procedure. He soon discovers that Forbes may have botched the work, leaving Miranda’s hormones more unstable and her alien side increasingly dominant. Driven by an overwhelming alien drive, Miranda seduces an innkeeper—another hybrid—but she kills him mid-act when she learns he is sterile. She later heads to a bar to seek more possible mates, stealing a provocative red dress from a bar singer.
Desperate to regain balance, Tom contemplates sedating Miranda to finish the job properly, and Forbes provides him with a near-lethal dose, warning that she is a “100% pure creature.” Their search takes them to a church, where Tom is ambushed by Azura; she resents the disruption Tom’s arrival has caused. He defeats her by dropping a heavy cross, leaving Azura badly wounded but not finished. Forbes then tracks Miranda to an abandoned warehouse, where she strips naked and reveals Forbes’s longstanding desire for her. Forbes gives in to his lust and allows Miranda to consummate their relationship, but once the act ends, she returns to alien form and suffocates Forbes by sliding her tongue down his throat. Tom later finds them.
Tom escorts Miranda back to Forbes’s house and learns, via X-ray, that a hybrid child is rapidly growing in her womb. Miranda laments that her humanity is dying and she does not want to be merely an alien. Azura returns in alien form, prompting Tom to fight her. In a tense confrontation, Miranda appears to kill Azura, but Azura rises again and fatally impales Miranda before Tom kills Azura with a shotgun. In her final moments, Miranda thanks Tom for giving her life before dying.
Overwhelmed by grief, Tom triggers a final, catastrophic self-destiny by turning on all the gas burners and tanks in Forbes’s house. He leaves as the structure erupts into a fiery explosion, ending a harrowing chain of events that began with a remarkable human talent and spiraled into a desperate struggle for survival.
